Topic 3 Flashcards
Describe the nucleus
A large organelle surrounded by a nuclear envelope which contains many pores.
The nucleus contains chromatin (DNA and proteins) and a nucleolus.
What is the function of the nucleus?
The nucleus controls the cell’s activities by controlling transcription of DNA.
DNA contains instructions to make proteins.
The pores allow substances to move between the nucleus and the cytoplasm.
The nucleus makes ribosomes.
Describe a lysosome
A round organelle surrounded by a membrane with no clear internal structure.
What is the function of a lysosome?
Contains digestive enzymes.
This are kept separate from the cytoplasm by the surrounding membrane and can be used to digest invading cells or to break down worn out components of the cell.
Describe a ribosome
A very small organelle that either freely floats in the cytoplasm or is attached to the rough endoplasmic reticulum.
It’s made up of proteins and RNA.
It has no membrane
What is the function of the ribosome?
The site where proteins are made
Describe the Rough Endoplasmic Reticulum
A system of membranes enclosing a fluid-filled space.
The surface is covered with ribosomes.
What is the function of the Rough Endoplasmic Reticulum?
Folds and processes proteins that have been made in the ribosomes.
Describe the Smooth Endoplasmic Reticulum
Similar to the RER but with no ribosomes
What is the function of the Smooth Endoplamsic Reticulum?
Synthesises and processes lipids
Describes the Golgi Apparatus
A group of fluid-filled , membrane bound, flattened sacs.
Vesicles are often seen are the edges of the sacs.
What is the function of the Golgi Apparatus?
It processes and packages new lipids and proteins.
It also makes lysosomes.
Describe the mitochondrion
Usually oval-shaped.
Double membrane - inner is folded to form cristae.
Inside is the matrix which contains enzymes involved in respiration.
What is the function of the mitochondrion?
The site of aerobic respiration, where ATP is produced.
They’re found in large numbers in cells that are very active and require lots of energy.
Describe a centriole
Small, hollow cylinders, made of microtubules.
Found in animal cells but only some plant cells.
What is the function of the centriole?
Involved in the separation of chromosomes during cell division.
Describe how proteins leave the cell.
1) Made at ribosomes
2) Ribosomes on the RER make proteins that are excreted or attached to the cell membrane. Free ribosomes in the cytoplasm make proteins that stay in the cytoplasm
3) New proteins made at the RER are folded and processed in the RER
4) They’re then transported from the RER to the Golgi apparatus in vesicles
5) At the golgi apparatus the proteins undergo further processing.
6) The proteins enter more vesicles to be transported around the cell.
What organelles can be found in Eukaryotic cells?
Nucleus Lysosome Ribosome RER SER Golgi apparatus Mitochondrion Centriole
What organelles can be found in Prokaryotic cells?
Pili
Mesosomes
Plasmids
Flagellum
Describe the cytoplasm in a prokaryotic cell.
Contains no membrane-bound organelles.
Has ribosomes but they’re smaller
What are Pili?
Short hair-like structures.
Help prokaryotic cells stick together
What are Flagellum?
Long hair-like structure that rotates to make cell move.
Not all prokaryotic cells have them.
What are mesosomes?
Inward folds in the plasma membrane.
Scientists are still debating what their function is.
Some believe they play a role in cellular processes others they’re artefacts that are proceduced when the cells are being prepared for viewing with an EM
Describe a light microscope.
- Use light to form an image
- Maximum resolution of 0.2 micrometers
- Can’t see ribosomes, endoplasmic reticulum or lysosomes
Describe an electron microscope.
- Use electrons to form an image
- Higher resolution than light microscopes
- Maximum resolution of 0.0002 micrometers
- Two types: Transmission or Scanning
Describe transmission electron microscopes (TEM)
- Use electromagnets to focus beam of electrons, which is transmitted through specimen
- Denser parts absorb more electrons which make them appear darker
- High resolution
- Can see internal structure of organelles
- Only used on thin specimans
Describe scanning electron microscopes (SEM)
- Scan a beam of electrons across specimen, knocks off electrons from specimen, these are gathered in a cathode ray tube to form an image
- Images show surface so can be 3D
- Can be used on thick specimens
- Lower resolution then TEMs
What are similar cells organised into?
Tissue
Name and describe 4 examples of tissue
1) Squamous
- single layer of cells lining a surface
2) Ciliated epithelium
- layer of cells covered in cilia
- found on surfaces where things need to be moved
3) Xylem
- transports water
- supports the plant
- contains xylem vessel cells and parenchyma cells
4) Cartilage
- connective tissue found in joints
- shapes and supports ears, nose and windpipes
